A propulsion system may include one or more traction motors to generate tractive output. For example, a propulsion system having one or more traction motors may be utilized in an off-highway vehicle (OHV) application, locomotive application, a marine application, a drilling application, etc. In one example, a locomotive vehicle having traction motors may perform dynamic braking in conjunction with air braking in order to slow the locomotive vehicle. By utilizing dynamic braking, the brake load on the air brakes may be reduced which, in turn, may reduce the wear on the air brakes thus extending their useful life.
During dynamic braking operations, the traction motors may generate electrical power that may be transmitted to a grid of resistive elements which may dissipate the electrical power in the form of heat. As dynamic braking operations are performed, the temperature of the grid of resistive elements may increase. Accordingly, a blower may be utilized to provide forced-air cooling to the grid of resistive elements. In one example, the blower is powered by a motor that is coupled to taps across the grid of resistive elements. As such, the blower operates whenever there is electrical power on the grid of resistive elements, such as during a dynamic braking operation. Since the blower is directly powered by electrical power from the grid of resistive elements, additional electrical power need not be generated specifically to power the blower.
However, various issues may arise with the above described configuration. As a first example, since the blower motor is directly connected to the taps across the resistive elements of the grid, the speed of the blower depends on the electrical power on the grid of resistive elements. As another example, the blower accelerates at a high rate whenever electrical power is suddenly applied to the grid of resistive elements, thereby producing high transients which may result in increased noise, vibration, harshness, and stress on the equipment.